For further information, the replacement cycle depends on how hard you push your team's quality up, and this in turn depends on your resources (token, money etc.) Generally, the maximum will be the contract end years (3,5,7,etc.) I believe you know players grow quickly only up to early to mid twenties. They will not increase in market values after this period. That's probably you want to know more. I think the most important consideration is whether the players are still useful for the team. But I can hint you that players usually grow much slower on reaching age 22.
That's correct for very low levels. But I would like hint the mangers who have not yet reached levels about 14 or 15 that shortage of money will gradually become an important issue. Building a stadium before the team cannot afford is important to keep the team to survive longer, well, without real money investment.